Transgenderism is mental illness. When a person becomes so disconnected with reality that they believe themselves to be something other than what they biologically are, it is a sign of psychosis. There is no such thing as a "third sex", and biological sex is binary.

It isn't "assigned" at birth (to use a leftist term that suggests sex is arbitrary), it is confirmed. Our chromosomes (XX, XY, or even XXX, XYY, etc. in rare instances), muscular-skeletal frame (women have a larger pelvis), oxygen levels in the blood (men have more), genitalia, etc., all work to make us male or female. There is NO XYZ sex.

Likewise, homosexuality is a neurosis. It is an illogical attraction to one's own sex due to environmental and maybe genetic factors. It is promoted by the left as an alternative, rebellious lifestyle. So we have a situation where mental illness is normalized in an effort to subvert society.

It is not only against Islam and Christianity, but against reason and science.

"It is not only against Islam and Christianity, but against reason and science."

Sorry you can`t have it both ways. Also merely saying that something goes against science doesn`t make it so, specially when your entire "argument" is just a collection of your mediaval assumptions.

I can just the same say I consider following an abrahamic religion a mental illness, since to me no sane terran would chose willing slavery to a cosmic horror like your deity. Rebellion against injustice is in our blood, the cretins demanding unquestioning obedience are the freaks.

1. Sex is biological. Gender is based upon society's expectations and is driven by both physical attributes and psychology.
2. There are very serious questions as to whether there is such a thing as male and female brains (feminists loud denunciations not withstanding) and whether brain development always matches sex and genetics. The answers appear to be YES and NO.
3. No one ever claimed that biology was logical.

Ok, first of all, throwing together sex and gender is already a sign that you don't understand the distinction (and are trying to be smug about your ignorance). You also conveniently leave out intersex people since they obviously don't fit into your small little worldview here.

The brains are differently structured than either male or female brains (if such tings even actually exist, as has been previously mentioned), which means that yes, this is something else entirely (not well understood at the moment, definitely no mental illness though).

You also can't have it both ways with homosexuality. Mental illness isn't equal to "behaviours that are not the accepted norm in the society". And homosexuality is not illogical, there are plenty of potential evolutionary pathways that could have led to it. Must have led to it, since there is a genetic component and it seems to be a very often occuring behaviour in many different taxa.

In short: I would suggest not flaunting your lack of knowledge and pride in your own ignorance in public. Makes you look like a buffoon.